Musical instrument



May 21, 1935.

J. H. HAMMOND, JR

MUSICAL INSTRUMENT Fig.1

INVENTOR.

ATTORNE).

ay 1935- J. H. HAMMOND, JR 2,001,722

MUSICAL INSTRUMENT Original Filed Aug. 15, 1929 2 Sheets-Sheet 2 4y I f v INV NTOR.

7 4 1 ATTORNEY.

Patented May 21, 1935 UNITED STATES MUSICAL John my; Hammond, in, Gloucester, Mass.

Application s m 15, 1929, Serial No. 380,155 Renewed June 11. 1932 Claims.

This invention relates to musical instruments, and more particularly to a musical instrument having a sounding board and a device for selectively amplifying the vibrations of said sounding bond.

. The invention also provides a regenerative cycle for picking up and amplifying the sounding board vibrations and returning the amplified vibrations to the sounding board. The vibrations are preferably picked up from anti-nodal points of the sounding boardwhere the amplitude is greatest in order that a maximum response may be obtained. The anti-nodal points of the sounding board may be determined by placing a small amount of finely divided material, such as sand, on the board and causing the board to vibrate at different frequencies. The arrangement of the particles which is produced by the vibrations of'the board indicates the location of the nodal and anti-nodal points. Means is also provided for manually controlling the amplitude of the vibrations whereby the volume of sound emitted from amusical instrument may be regulated at will.

The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended advantages, the mode of its operation and the manner of its organization may be better under- 85 stood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which Fig. 1 is a side elevation partly in section of a piano with a diagrammatic showing of the amplifying device associated therewith;

Fig. 2 is a bottom plan view of the piano;

Fig. 3 is a detailed view of a modified form of pick-up device;

Fig. 4 is a diagrammatic view of the pick-up device and amplifier, including a wave filter;

Fig. 5 is an enlarged sectional view of a modi-, fied form of the invention utilizing a condenser loud speaker.

Like reference characters denote like parts in the several figures of the drawings.

In the following description and in the claims parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts-as the art will permit. a

In a form of the invention shown in Figs. 1 and 2 a grand piano III is shown as provided with the usual sounding board I I, frame l2 and strings l3. Below the sounding board I I are diagonal braces ll carrying transverse members IS on 5 which are mounted a plurality of pick-up devices I0, I! and it, which may be of any well known construction. The armature or moving parts of these pick-up devices are connected by rods Ii, 22 and 23 respectively to the sounding 10 board ll. Pick-up devices l6, l1 and I8 may be mounted at various positions on the sounding board, but are preferably located at anti-nodal points for the various frequencies with which the sounding board is actuated in order that. a 15 maximum response may be obtained.

The windings of the electromagnetic pick-u devices I6, l1 and II are connected to the primales of transformers 24, 25, 28, the secondaries of which are connected topotentiometers 21, 28 and 28 respectively. These potentiometers are connected in series to a fourth potentiometer 3| the moving contact 32 which is mounted on but insulated from an "arm 33, which is pivoted at 34 to the frame of the piano. This arm is engaged 25- by a collar. 35 mounted on the shaft 36 which is operated by the loud pedal 3] so that when the loud pedal is depressed the shaft 36 will be elevated, thus rotating the arm 33 in a clockwise direction. A spring 38 returns this arm to its 80 initial position when the loud pedal 31 is released. hereto, the invention itself, as to its objects and Contact 32 and one'side of potentiometer 3| are connected to the input "of an audio frequency amplifier II, the output of which is connected by conductors ii 'to a loud speaker 53 which is mounted on the sounding board II. The dead weight of speaker 53 may be partly supported by spring 54 which is mounted on bracket 55 forming a part of the frame of the piano.

In the above described system, vibrations of 4 strings II of piano is cause vibrations of sound ing board ii. These vibrations are picked up by a pick-up devices II, 22 and 23, are amplified by amplifier ll, and are impressed on loud speaker v 53, which is carried on or adjacent the sounding 45 board. The sounding board is provided with an aperture (not shown) above the loud speaker through which the sound waves'are propagated.

The compressional waves produced in the atmosphere by speaker I! serve as a mechanical cou- 7 pling between the loud speaker and the sounding board and cause further vibration ofsaid sounding board.

It is evident therefore that by suitably controlling the amount of pick-up and amplification 55 the sounding board can be made to continuously vibrate in response to a given note or the duration of the vibration may be controlled at will. Speaker 53 and amplifier 4i may be of any desired form and are not shown in detail.

Potentiometers 27, 28 and 29 permit the energy picked up from various portions of the sounding board to be selectively controlled so that the amplification of the various notes may be controlled at will. Potentiometer 3| determines the value of the input of amplifier ll and accordingly controls the overall amplification of the entire group of pick-ups. The number of pick-up devices have been shown as three for purpose of illustration, but it is to be understood that any desired number may be employed.

The modified form of pick-up device 6 I, as shown in Fig. 3, is supported from diagonal member I4. Said pick-up device is provided with an armature 62 which is connected as by rod 63 to the sounding board II. The winding of pick-up device 6| is connected to the primary of the transformer 24, the secondary of which is connected in the amplifier circuit in a manner pointed out in connection with Fig. 1.

When the loud pedal of the piano is depressed thereby lifting dampers. on the strings, there is tendency of the vibrations to be built up by the regenerative action above described to an unde-- sired value. For this reason potentiometer Si is shown as connected to the loud pedal in such a way that the depression of the pedal decreases the energy fed into the amplifier 4 I, thereby providing an automatic check which prevents undesirable regeneration when the loud pedal is depressed.

In the modified form of the invention shown in Fig. 4, the pick-ups are assumed to be identical with those shown in Fig. 1. The secondaries of transformers 24, 25 and 26 in Fig. 4 are led through band-pass filters II, I2 and I3 to the input circuit of amplifier tubes I4, I5, and I6. Band-pass filters II, I2 and I3 are preferably so adjusted that each filter passes, with approximately equal intensity, the various notes picked up by the pick-up devices associated therewith.

The output of tubes II, I5 and I6 are impressed upon the input of the power amplifier tube 11 by means of any desired coupling circuit. Said tubes have been shown as coupled by means of resistances I8 and condenser I9, although it is obvious that various other types of coupling may be employed if desired. The output circuit of tube II is led through conductors 5| to speaker 53 in the manner pointed out in connection with Fig. 1.

In the system of Fig. 4 the wave filters eliminate the undesired frequencies and pass only those frequencieswhich are picked up by the various pick-up devices associated with the sounding board. This system is therefore capable of producing, a particularly pure tone.

In Fig. 5 the invention is shown as applied to a condenser loud speaker comprising a rigid metallic plate IIO which may be secured to sounding board Ii by suitable means such as screws Ill. Screen III is positioned over plate III! and likewise secured to the sounding board. A dielectric I I2, of flexible insulating materiaL'such as rubber, is positioned over screen III and is held in positionby ring I I5 which issecured to the sounding board as by bolt Iii. A covering of conducting material such as foil I I3 is applied over dielectric H2 in any suitable manner and is adapted to vibrate with respect to plate I III as the potential difference between the two plates is altered. The

operation of a condenser speaker, however, is well known and will not be described in detail. Wires 5i comprising the output of the amplifiers above described may be connected to plate H0 and foil I I3 as by screws I lll and clip I II respectively.

It is to be noted in each of the systems above described, the vibrations of the sounding board are picked up amplified and fed back into the loud speaker which is so positioned that it may react on the sounding board. Mechanism is also provided for controlling the amplitude of the oscillations and the amount of amplification whereby various tonal effects may be produced at the will of the operator.

While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. In combination with a musical instrument having a sounding board, a pick-up device associated with said sounding board and adapted to pick-up energy of vibration therefrom, means for amplifying said energy and means for applying said amplified energy to said sounding board so as to decrease the damping of the vibrations of said board.

2. In combination with a musical instrument having a sounding board. a pick-up device associated with said sounding board and adapted to pick-up energy of vibration directly therefrom, means for amplifying said energy and means for applying said amplified energy to a loud speaker mounted adjacent said sounding board in a position to react directly therewith so as to decrease the damping of the vibrations of said board.

3. A musical instrument having a sounding board, a plurality of pick-up devices mounted at anti-nodal points of said sounding board, ampliying means associated therewith, and means associated with said amplifying means for retruning the amplified energy of vibration to said sounding board.

4. A musical instrument having a sounding board, a plurality of pick-up devices mounted at anti-nodal points of said sounding board, amplifying means associated therewith, means associated with said amplifying means for returning the amplified energy of vibration to said sounding board, andmeans for selectively controlling the amount of energy transferred from each of said pick-up devices to said amplifying means.

5. A musical instrument having a sounding board, a plurality of pick-up devices mounted at anti-nodal points of said sounding board, amplifying means associated therewith, means associated with said amplifying means for returning the amplified energy of vibration to said sounding board, and means for controlling the amount of amplification of said energy whereby excessive regeneration may be avoided.

6. In a piano having a sounding board, pickup devices located at anti-nodal points thereof, an amplifier for amplifying-the energy of said pick-up devices, means for separately controlling the energy of each pick-up device, means associated with the loud pedal of said piano for controlling the energy applied to said amplifier, and means for returning the amplified energy t0 said sounding board.

7. In a piano having a sounding board, pickup devices located at anti-nodal points thereof, an amplifier for amplying the energy of said pickup devices, means for separately controlling the energy of each pick-up device, means associated with the loud pedal of said piano for controlling the energy applied to said amplifier, and means for returning the amplified energy to said sounding board comprising a loud speaker mounted adjacent said sounding board and connected to the output circuit of said amplifier.

8. In combination with an instrument having a sounding board, a plurality of pick-up means associated with said sounding board, an amplifying device associated with each said pick-up means and a band-pass filter associated with each of said amplifying devices whereby only desired frequencies are amplified, and means for returning the amplified energy to said sounding board.

9. In a piano having dampers on the strings thereof operated by the loud pedal, means for operating said piano regeneratively, and a device controlled by said loud pedal for eliminatinging excessive regeneration when the pedal is operated.

10. In a piano having dampers and means for removing the effect of saiddampers, an amplifier, means for feeding vibratory energy from a part of the piano into said amplifier, means for feeding the output of said amplifier back into the piano and devices controlled by said first mentioned means for controlling the energy fed back into the piano to eliminate excessive regen-' eration.

11. In a piano having portions adapted to vibrate at different frequencies, a plurality of separate pick-up devices picking up said different frequencies, individual band filter circuits associated with said pick-up devices respectively and a translating device fed by said filter circuits, said filter circuits passing only frequencies corresponding to those picked up by their respective pick-up devices.

12. In combination, a musical instrument having parts adapted to vibrate at different frequencies, a pick-up device for picking up said frequencies, a sound propagating element, amplifying means between said pick-up device and sound propagating'element, regenerative means to feed back energy from the output of said amplifying means to its input, and means for preventing the regeneration of certain frequencies.

13. In a musical instrument, a vibratable element, means to cause said vibratable element to vibrate at different tone frequencies to initiate musical notes of different pitch, a pick-up device for picking up the said different tone frequencies, a sound propagating device fed by said pick-up device, and filter devices for selectively determining the tone frequencies fed to said sound propagating device by said pick-up device, whereby to modify the sound initiated by said vibratable element.

14.-In a piano, a plurality of vibratable portions vibratable at different tone frequencies, means for setting said portions into simultaneous vibration to produce simultaneously tones of different pitch, a plurality of pick-ups corresponding to said portions for separately picking up the different tone frequencies, amplifier devices fed by said pick-ups, loud speaking devices fed by said amplifier devices, and separate filter devices, one for each pick-up for determining the tone frequencies fed to said amplifier devices by its corresponding pick-up.

15. In a musical instrument, a plurality of vibratable portions vibratable at different tone frequencies, means for setting said portions into simultaneous vibration to produce simultaneously tones of different pitch, a plurality of pick-ups corresponding to said portions for separately picking up the different tone frequencies, a sound propagating device fed by said pick-ups, and separate filter devices, one associated with each pickup for determining the tone frequencies fed to said sound propagating device by its corresponding pick-up.

16. In a musical instrument, vibrating devices for producing musical notes, amplifying devices fed by said vibrating devices, sound propagating devices fed by said amplifying devices, means for regeneratively connecting the output of said amplifying devices to the input thereof, and means for eliminating excessive regeneration.

1'7. In a piano having a plurality of strings tuned to different frequencies and a hammer system for setting said strings into vibration, electric pick-up devices for picking up vibrations froin said strings, an amplifier fed by said pick-up devices, a loud speaker fed by said amplifier, and electric filter devices for selectively determining the tone frequencies fed to said loudspeaker by said pick-up devices to remove undesired sounds. 

